mulit: use kvdb.Backend for the kv payment db

Instead of the ChannelState struct we now use the kv backend
interface for the payment kv database.

payments/db/options.go

@@ -0,0 +1,30 @@
+package paymentsdb
+
+// StoreOptions holds parameters for the KVStore.
+type StoreOptions struct {
+	// NoMigration allows to open the database in readonly mode
+	NoMigration bool
+
+	// KeepFailedPaymentAttempts is a flag that determines whether to keep
+	// failed payment attempts for a settled payment in the db.
+	KeepFailedPaymentAttempts bool
+}
+
+// OptionModifier is a function signature for modifying the default
+// StoreOptions.
+type OptionModifier func(*StoreOptions)
+
+// WithKeepFailedPaymentAttempts sets the KeepFailedPaymentAttempts to n.
+func WithKeepFailedPaymentAttempts(n bool) OptionModifier {
+	return func(o *StoreOptions) {
+		o.KeepFailedPaymentAttempts = n
+	}
+}
+
+// WithNoMigration allows the database to be opened in read only mode by
+// disabling migrations.
+func WithNoMigration(b bool) OptionModifier {
+	return func(o *StoreOptions) {
+		o.NoMigration = b
+	}
+}